A sliding-mode-based active fault-tolerant control for robust trajectory tracking in quad-rotors under a rotor failure

In this article an active fault-tolerant control (FTC) is developed for the tracking problem in a quad-rotor under the effects of a rotor failure and external disturbances. Such a strategy is composed of a finite-time sliding-mode observer, which estimates the full state from the measurable output and identifies uniformly bounded and Lipschitz disturbances. The failure scenario is analyzed in order to identify how it affects the dynamics. It is assumed that the failure has been isolated. The FTC design is composed of PID and continuous high-order sliding-modes controllers that allow the yaw angular velocity to remain bounded and the position tracking to be achieved even in the presence of some external disturbances. The closed-loop stability is formally proven. Numerical simulations show the performance of the proposed control strategy.